This application claims the priority of German patent document 197 20 903.3, filed May 17, 1997, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a system for parallel alignment of the axes of a thermal image apparatus.
The guidance of missiles is normally coordinated with the graticule of a telescope through which the launcher sights the target. If a nightviewer is added to the launching system, its optical axis must be parallel to that of the telescope, as defined by the graticule. The required precision of typically 0.1 mrad is very difficult to set mechanically and, under military environmental conditions, is even more difficult.
It is known simply to equip the nightviewer with magnification, and to position it as an attachment in front of the telescope in order to use the graticule of the telescope also in night operations. However, this process requires that, in the nightviewer, the IR input axis and the visible output axis are disposed in parallel within &lt;0.1 mrad, and remain so. An embodiment of this state of the art is illustrated in FIG. 2. The IR beam path and the visible beam path extend largely along the same optical elements so that relative axis drifts of the components are eliminated. The mirror M7 and the beam splitter D3 must be disposed stably relative to one another, but may drift jointly. By means of such an arrangement, the parallel alignment of the axes is held within 0.1 mrad in a limited temperature range, at considerable expenditures.
Furthermore, in the arrangement of FIG. 2, the thermal image apparatus must be designed specifically for this application. Thus, it is not possible to use one of the many available observation nightviewers. Also, modern nightviewers have a monitor or an LCD as a display and no longer have LED's which can be utilized only in a precise IR detector configuration and number of detectors. However, it is known that these furnish only relatively dark images. The utilization of joint beam paths in the IR band and in the visual band is therefore no longer possible.
It is an object of the present invention to provide a system of the above-mentioned type in which the IR input axis is fully automatically aligned in parallel with to the visual output axis of the thermal image apparatus, also for nightviewers which are conceived only for observation purposes.
This and other objects and advantages are achieved by the alignment system according to the invention in which the IR beam path and the visible beam path extend along the same optical elements. A luminous point/four-quadrant sensor unit which is adjusted with precise and stable axes, is assigned to the IR radiation and visual radiation in front of the display (LCD); and an imaging arm, which can be swivelled into the IR beam path or is stationary and has a ridge mirror and a plane mirror, or only a beam splitter, is arranged in front of the viewing lens system.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.